There has been a dramatic rise in sales of nutrient-rich "superfoods" as more people learn of their health benefits, new research suggests.

The products which have soared in popularity include spinach, salmon and soy according to data collected by market analyst AC Nielsen.

Blueberries enjoyed the biggest surge in popularity, the figures showed - up 132% in the last two years.

Better marketing by retailers was thought to have caused the upturn.

The research showed that Britons spent £95m on blueberries - renowned for their anti-aging properties - in the past two years.

'Value for money'

Nielsen business insight director Jonathan Banks said major retailers were spending more on marketing such foods, resulting in greater awareness of their health benefits.

"Blueberries contain antioxidants which help with circulation, keeping the heart healthy and maintaining youthful-looking skin.

"These are all important to today's health and youth-conscious consumer," he said.

He added that many shoppers saw superfoods as value for money.

SUPERFOODS

Blueberries: Sales up 132% in the past two years

Spinach: Sales up 31% since 2005 to a total of £42m in the past year

Salmon: Sales up 31% in two years to a £450m spend in the past year

Green tea: Sales up 45% with more than £16m spent in the past two years

Soy: Up 50% since 2005 to a spend of £70m in the past year

"What's going on at the moment for shoppers is that food and drink has never really been better value for money than it is now," he said.

"So if you are faced with the choice of spending £1.30 on something instead of £1, that extra 30p for that extra quality, that extra freshness, those extra benefits, might be something you could quite easily do."

Spinach sales rose to £42m in the past year - up from £32m in the year from May 2005.

Over the same period salmon sales increased 31% to reach £450m.

Other superfoods which have seen sales rise include shelled walnuts - up 30% in the last two years - and fresh beans, which rose 13% over the same period.

Sex drive

Green tea sales rose by 45% to more than £16m in the past two years.

Soy also performed well, with annual sales of non-dairy soy drinks rising 50% since May 2005 to more than £70m.

So-called "superfoods" are those which have a high nutritional value. There is no definitive list but the most commonly cited such foods are blueberries, broccoli, spinach and green tea.

It is claimed that superfoods can maintain young-looking skin and protect against cancer and heart disease.